Mouse wheel click changing active sim

Hi all,

 I looked everywhere to find if anyone ever had this problem but found nothing.

I use my the sims 3 camera control so I use the mouse wheel click to rotate the camera, but out of nowhere clicking the mouse wheel is changing my active sim! That had happened before and the same way it started it stopped.

I looked on the settings everywhere to see it there was an option about it but could not find it.

That’s sooo annoying, it makes impossible to play with more the one sim in your family!

Please help me find a way to change that!